Underwater acoustic transducers with wide bandwidth are desirable for underwater communication, sonar, or noise, signal-making and jamming applications. It is well known to those skilled in the art, that a broadband transducer may be achieved by a plurality of cylindrical transducers to cover a desired frequency range, however in comparison with the subject approach, the former broadband transducers provide outward radiation that is largely directional.
Many broadband electroacoustic transducers have been described using a plurality of cylindrical ring transducers elements each having different resonance frequencies to achieve a broadband coverage. For example, U.S. Pat. No. 2,439,927 by Krantz describes a plurality of magnetostrictive cylindrical transducers aligned coaxially in decreasing size. Such an approach employing cylindrical piezoelectric ceramic elements is common today to those skilled in the art whereby a sound is radiated predominantly in a direction radially outward to achieve an omnidirectional radiation in one plane. Such a beam pattern maybe considered toroidal in shape. U.S. Pat. No. 4,916,675 by Hoering also describes a broadband acoustic transducer by using a plurality of transducer rings although of the same diameter each having different resonance frequencies. U.S. Pat. No. 4,439,847 by Massa describes a means to achieve a broadband electroacoustic transducer employing a plurality of cylindrical transduction elements whereby the use of reflectors causes the primary radiation to be directed on axis of comprising coaxial elements. Such a beam may be described as conical. U.S. Pat. No. 6,215,231 by Newnham et al. describes an electroactive ceramic hollow sphere having access holes to enable the passage of instrumentality. U.S. Pat. No. 6,768,702 by Brown and Aronov describes a method for obtaining broader bandwidth directional electroacoustics transducers by combining the use of multimode excitation of cylinders (or spheres) with conformal acoustic baffles.